The present invention concerns a gradient optical fiber with an optimized profile for index of refraction.
The band width of multimode glass fibers for data transmission is limited by the fact that differences in transit time will occur between the many modes that can be propagated in each fiber. These differences between transit times can be kept small by giving the fiber a parabolic profile for the index of refraction. Since the form of the index of refraction profile is generally dependent on the wavelength of the light and since the light to be transmitted is not strictly monochromatic, the transit time equalization is made more difficult.
To date, the best attempt at optimizing the index of refraction profile while taking a profile dispersion into account has been disclosed in an article by E. A. J. Marcatili in The Bell Systems Technical Journal, Vol. 56, No. 1, Jan. 1977, pgs. 49-63. By adapting the index of refraction profile to a predetermined profile dispersion, the process of Marcatili aims to ensure that group transit time differences only exist between modes of differing propagation constant and not, as in the general case, between modes with the same propagation constant, as well.